fix: pin starlette==0.50.0 to prevent crash on Starlette 1.0 (removed TemplateResponse compat shim)

Starlette 1.0.0 released and removed the backwards-compatibility shim for
the old TemplateResponse(name, context) call style. Without the shim, the
context dict is passed as the template name → jinja2 LRU cache key →
TypeError: unhashable type: 'dict' on every page load.

Gradio 4.44.1 uses the old positional form, so we pin starlette<1.0.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

requirements.txt

@@ -7,6 +7,7 @@
 # ===========================================
 gradio==4.44.1
 huggingface_hub==0.26.2  # Pin for Gradio 4.44.x compatibility (HfFolder removed in 0.27+)
+starlette==0.50.0        # Pin <1.0: Starlette 1.0 removed TemplateResponse compat shim (dict-as-name crash)
 python-dotenv==1.0.1
 requests==2.31.0
 beautifulsoup4==4.12.3